As I Was Browsing Your Article I Wanted To Sample Comment. You Have Disabled Public Comments, People Have To Register On Your Site To Comment.
When You Goto
Discussion Settings Page Look At The Option Other comment settings
And See The Options There.
MY Recomendations
1. Check The Box (Comment author must fill out name and e-mail)
2. Uncheck The Box (Users must be registered and logged in to comment)
3. You Chose (Automatically close comments on articles older than _ Days)
4. Check The Box (Enable threaded (nested) comments [Recomended 2] _ levels deep)
5. You Chose (Break comments into pages with top level comments per page and the page displayed by default
Comments should be displayed with the comments at the top of each page)
Goto Before a comment appears And Change
1. You Chose (Comment must be manually approved)
2. Better If Checked (Comment author must have a previously approved comment)
Continue This Thread If You Still Have Issues